This invention relates in general to multi-spindle machines. Specifically, this invention relates to a multi-spindle machine having attachments for pick-up and back machining operations.
Multi-spindle machines are known in the prior art. Multi-spindle machines are used to mass produce standardized types of components. A multi-spindle machine typically has several work stations at which machining operations are performed. A piece of raw stock, such as a bar stock, enters the machine at a first station and as the machine indexes, various machining operations are performed. Once the station is indexed completely through the machine, a completed part is formed. The part is released, and the process is repeated for that station with a new piece of raw stock. An advantage of multi-spindle machines is that all stations in the machine are producing parts simultaneously, resulting in high production.
Multi-spindle machines (also referred to as multiple spindle machines) typically have a large indexing spindle drum with four, five, six or eight work spindle stations thereon. Each of the stations carries a work piece. Generally in all but one of the stations, where a new piece of stock enters, a machining operation is performed. After each machining operation is completed, the drum is rotated so that each work piece moves sequentially through the locations where the various machining operations are performed. Machining operations that are typically performed at a multi-spindle machine include milling, turning, and threading.
Most multi-spindle machines are very efficient in terms of producing standardized parts at a high rate. However, one drawback associated with a multi-spindle machine is that the entire machine operates off of a single main motor. The main motor simultaneously drives all of the devices and processes in the machine. Multi-spindle machines typically include one or more timing shafts with cams for the coordination of multiple machine operations.
There is always a risk that one of the mechanisms within the machine will not function properly. If such a malfunction should occur and not be detected by an operator in time to shut the machine off, the machine will continue with its next cycle. In such a case, an attempt by the machine to index to its next position could cause severe damage. This is why it is common for an operator to be required to closely monitor multi-spindle machines.
Typically, the speed of multi-spindle machines changes from high to low speed and back again during the course of the operating cycle. High speed is normally used for times in the machine cycle when critical machining operations are not occurring. High speed operation is desirable when the stations are indexing, or when the tools are moving toward or away from the work pieces and are not performing work thereon. Low speed operation is generally used when the tools in the machine are forming the metal. Any attempt to operate the machine at a high speed when such forming work is being performed is likely to cause a problem or jam the machine.
In many multi-spindle machines at the final station the completed work piece is cut off from the stock. The completed work piece is dropped onto a conveyor or other device to move it away from the machine. It is common to have to perform additional operations on the completed part before it is ready for use. These additional operations are often done by hand or in other machines and add substantial cost to making the part. In many machines the movement of the work piece after cut off is unpredictable and may result in nicks on the ejected work piece. Therefore, work pieces sometimes become damaged and unusable. Furthermore, because the work piece is released from a rotating collet, large work piece catchers are required in order to ensure catching of the falling work pieces. Additionally, the large catchers have to be situated in a crowded tool zone, which often makes it difficult to control the cut off part and avoid damage to parts and other machine components.
In some multi-spindle machines pick-up attachments are available for pick-up of work pieces in the station where the completed work piece is cut off from the stock. Sometimes back machining operations in which a single minor back machining operation after cut off, such as finishing, reaming, chamfering, recessing, and deburring is performed by the machine. A pick-up attachment may include a dead length collet type with the collet operated by twin toggles controlled by a special cam mounted on the main camshaft in front of the main drive housing. The collet may be attached to a pick-up spindle. A pick-up collet is able to grip and eject the work piece. The movement of the pick-up attachments is typically set with the timing of the multi-spindle machine.
The pick-up spindle has one rotational speed which is generally mechanically gear driven. The rotational speed is set one to one with the spindle speed. During a pick-up operation, the pick-up spindle with the collet is moved axially up to the workpiece and is rotated at the same speed as the workpiece. The collet is moved over the work piece to hold it so that the work piece may be cut off. Later the work piece may be dropped in a relatively controlled manner from the pick-up spindle. However because the pick-up spindle is rotating the work piece there is still often difficulty preventing damage to work pieces and machine components when the part is released by the pick-up spindle.
The axial movement of the pick-up spindle is generally controlled by mechanically driven cams and levers. Timing changes are difficult because a mechanical cam must be altered or adjusted. Movement is limited by the travel of the cams and related levers. The cam actuated movement of a pick-up spindle is often restricted to less travel than would be desirable. Often the limited ability to control and move the pick-up spindle necessitates that additional operations on parts be done in subsequent operations in other machines or by hand.
In a back machining or forming operation of the prior art multi-spindle machines the pick-up and back machining operations are controlled by the mechanical cams and actuating devices in the machine. Thus, back machining operations are limited. Every work piece is picked up at the same position and speed, and any back machining operation is done at the spindle speed of the spindle from which the part has separated by the cut off operation. The operations are repeatedly performed based on the multi-spindle machine""s timing device. The pick-up spindle collet is constantly rotating at the speed of the work piece collet. This pick-up collet is axially driven by cams and levers to position the collet over the work piece held by the work spindle. The pick-up spindle collet grippingly engages the work piece which is then cut from the remaining stock. The rotating or spinning work piece may then have a back machining operation performed thereon. An ejector plunger may be used for removal of the work piece from the pick-up spindle. The pick-up spindle is axially retracted toward a stationary ejector plunger so that the work piece is pushed out of the pick-up collet by the ejector plunger. However, the work piece is ejected from the collet while it is still rotating. Therefore, large work piece catchers are required to catch the ejected rotating work piece because of its unpredictable drop location.
A disadvantage with the prior art multi-spindle machines is that the rotational speed and the axial movement of the pick-up spindle are limited. Thus, the types and character of back machining operations are limited. For example, because the prior art pick-up spindle is constantly rotating, the drilling of a hole transversely through the work piece while it is held in the machine is not readily achievable. Similarly the performance of multiple back machining operations in the multi-spindle machine after part cut off is not achievable because of the limited ability to control part position and machining speeds.
Another disadvantage with prior art multi-spindle machines is that the axial and rotational pick-up position of the collet cannot be variably selected. Nor is the pick-up position always consistent and reliable. This leads to inconsistent back machining operations on the work pieces.
There exists a need for a multi-spindle machine having an arrangement that can overcome the disadvantages associated with the prior art pick-up and back machining operations. Thus, there exists a need for a multi-spindle machine having a system that can perform pick-up and back machining operations at controlled variable speeds and with a wider range of controlled part movements. Particularly, such a system would be preferably suited for retrofit on a Wickman, National Acme and New Britain multi-spindle machine.
It is an object of the present invention to provide a multi-spindle machine with improved pick-up and back machining operations.
It is a further object of the present invention to provide a multi-spindle machine with a pick-up spindle that may be driven at variable rotational speeds clockwise and counterclockwise.
It is a further object of the present invention to provide a multi-spindle machine with a pick-up spindle that may be rotationally stopped.
It is a further object of the present invention to provide a multi-spindle machine with a pick-up spindle that may be driven to variably selected linear axial positions.
It is a further object of the present invention to provide a multi-spindle machine with a pick-up spindle that may be driven at variable linear axial speeds.
It is a further object of the present invention to provide a multi-spindle machine with a pick-up spindle that may be stopped in a selected linear axial position.
It is a further object of the present invention to provide a multi-spindle machine with a pick-up spindle that may be stopped in a selected rotational orientation position.
It is a further object of the present invention to provide a multi-spindle machine having a system that can perform pick-up and back machining operations at selectively variable rotational and axial speeds and movements.
It is a further object of the present invention to provide a multi-spindle machine capable of being retrofit to enhance the pick-up and back machining operations.
Further objects of the present invention will be made apparent following the Best Modes for Carrying Out Invention and the appended claims.
The foregoing objects of the present invention are accomplished by a multi-spindle machine that performs pick-up and back machining operations. The multi-spindle machine has a pick-up attachment including a pick-up spindle and collet. The pick-up spindle has variable rotation capabilities. The pick-up spindle may be rotationally driven at different speeds. For example, the pick-up spindle may be rotationally driven at either of two speeds. One speed may be matched one to one with the work spindle for xe2x80x9czeroxe2x80x9d relative speed, such as for use in initially gripping the work piece during cut off. The second speed may be at a useful ratio of the zero relative speed, such as a speed that may be better suited to further machining operations. The capability of using a second speed enhances the capability of the machine to perform back machining operations. A brake may be used to stop the pick-up spindle. With the pick-up spindle stopped, the collet may be opened and the part ejected more reliably and accurately. This reduces the risk of damage to the parts and to components of the machine.
In embodiments of the invention the pick-up spindle may be rotationally driven using plural driving gears with respective clutches, and a brake. The arrangement of different gears enables the pick-up spindle drive shaft to be selectively rotationally driven at different speeds. As previously discussed, one speed may be useful for initially gripping the work piece, another speed may be useful in back machining operations. The clutches enable the gears to be operatively engaged or disengaged in driving relation with the pick-up spindle shaft.
The arrangement of different gears, clutches, and brake may be operatively controlled by a controller. The controller may be operatively connected to one or more movement synchronization sensors such as an encoder. The encoder may be arranged on the multi-spindle machine so that it can be used by the controller to determine which speed to drive the pick-up spindle collet. For example, the controller may be used to engage a clutch to match the speed of the drive shaft with the speed of the work spindle collet. Thus, the pick-up collet may be rotated at the same speed as the work spindle collet and thus the work piece. The controller may then disengage the first clutch and engage another clutch to drive the pick-up spindle at a speed suitable for a back machining operation. Of course the controller may be used to perform other functions. For example the controller may operate to disengage the clutches and to engage the brake. The brake enables the pick-up spindle to be stopped. With the pick-up spindle stopped the pick-up collet may be opened and the completed work piece may be ejected.
In alternative embodiments the pick-up spindle may also be rotationally driven using a motor arrangement, such as a servo motor or an air motor. A brake may also be used. The servo motor is operated responsive to a controller and is able to rotationally drive the pick-up spindle shaft at different speeds. As previously discussed, one speed may be useful for initially gripping the work piece, while other speeds may be useful in back machining operations. The servo motor may be placed in operative connection with the pick-up spindle drive shaft to move it at a plurality of rotational speeds responsive to the controller. The controller may be operatively connected to one or more movement synchronization sensors such as an encoder. The encoder may be arranged on the multi-spindle machine so that it can be used by the controller to determine the speed of the work piece holding collet. The controller is able to control the speed of the pick-up spindle electronically. Hence, the controller is able to match the speed of the servo motor with the speed of the work spindle collet. Thus, the pick-up collet may be rotated at the same speed as the work spindle collet and thus the work piece during part cut off. Of course the controller may be used for other purposes. The controller which controls rotational movement of the pick-up spindle may also be operatively connected to a brake. The brake enables the pick-up spindle to be stopped. During stoppage of the pick-up spindle the pick-up collet may be opened and the work piece component may be ejected.
The pick-up spindle may be linearly driven along its axis of rotation responsive to the controller. This may be done using a drive mechanism which is selectively movable. The drive mechanism may include air cylinders with solenoids and a programmable electronic output device. In an exemplary embodiment the drive mechanism includes a servo motor. The servo motor is able to axially position the pick-up collet and the work piece engaged therewith at different locations. The servo motor is also able to axially move the pick-up spindle shaft at different speeds. The different locations to which the pick-up spindle is moved may include a plurality of back machining stations and a work piece drop station. The controller may be operatively connected to an encoder arranged on the multi-spindle machine or other device suitable for sensing the axial position of the pick-up spindle. The controller is operative responsive to signals from the encoder to control the servo motor. Thus, the controller is able to control the axial movement of the pick-up spindle. Hence, the controller is able to determine and control the axial speed and position of the pick-up collet during pick-up operations and back machining operations. Of course the controller may be used for other purposes. The controller for the linear movement of the pick-up spindle may be operatively connected to one or more electronic output devices. Such outputs may operate to control other components of the multi-spindle machine.
It should be understood that in other embodiments of the invention a pick-up spindle may be moved responsive to other axially positioning devices. However, a motor, such as a servo motor, can be used to more accurately control the positioning of the pick-up spindle. Furthermore, use of a motor provides more accurate control of the axial speed of the pick-up spindle.
An exemplary embodiment of a multi-spindle machine performing pick-up and back machining operation of the present invention, may include the following steps: matching the rotational speed of the pick-up collet with the speed of the work spindle collet; positioning the pick-up collet over the work piece; grasping the work piece with the pick-up collet; cutting the work piece from the remaining stock; adjusting the rotational speed of the work piece; axially moving the work piece to a back machining position; back machining the work piece; axially moving the work piece to an eject position; stopping the rotational speed of the work piece; and ejecting the work piece into a work piece catcher. The method may further include controlling the axial speeds and rotational positions of the work piece as operations are performed. Of course it should be understood that the rotational and the axial movements and speeds of the pick-up spindle may be controlled as necessary to perform the desired pick-up, back machining, and drop operations.